Inert simulant composition for a plastic bonded explosive



United States Patent 3,457,329 INERT SIMULANT COMPOSITION FOR A PLASTICBONDED EXPLOSIVE Wallace E. Silver and Jack Sherman, China Lake, Calif.,

assignors to the United States of Amercia as represented by theSecretary of the Navy N0 Drawing. Filed Feb. 21, 1968, Ser. No. 707,924Int. Cl. C08f 29/20 U.S. Cl. 260-857 2 Claims ABSTRACT OF THE DISCLOSUREAn inert simulant formulation for a high explosive composition which hasthe density, thermal conductivity, and thermal coeflicient of expansionof the duplicated explosive and also possesses equivalent physicalstrength, rigidity under stress, and machinability. This formulationprovides inexpensive and safe testing of mock missiles and rocketwarheads and other components utilizing high explosives.

Background of the invention The present invention is for an inertsimulant composition for a high explosive.

In the field of explosives inert simulants or duplications thereofhaving the necessary characteristics for their practical use in mockwarheads and similar missile components using high explosives are notknown. A few compositions duplicating only one or two properties of theexplosive were found but proved unsuccessful because density was theproperty most frequently simulated. A typical explosive simulantconsisting of castor wax, ferrous oxide, calcium sulfate and wood rosinsimulated only the pressed density and had the great drawbacks ofmelting at 187 F. Any elfective valuation of arerodynamic heatingeffects on -a mock missile war head containing this composition wasprecluded.

Summary of the invention This invention is for an inert simulantcomposition for plastic bonded explosives which comprises a mxture ofpolytetrafluoroethylene (sold under the trade name Tef- Ion"), a linearpolyamide (sold under the trade name Zyte1) and entaerythritol. Itduplicates the linear coefficient of thermal expansion and thermalconductivity of a plastic bonded explosive in addition to density and isalso of comparable strength, easily bonded to other surfaces and readilymachinable. Accordingly, this invention solved the longstanding need foran inert simultant composition possessed of suflicient of thecharacteristics of high explosives for use in effectively evaluatingmock missile warheads and other devices which contain or use highexplosives. This invention also provides an economical, practical andsafe simulant for development and testing situations involving highexplosive.

Description of the invention (1) Density, 1.700i0.010 gms./cc. (2)Linear Coeflicient of Thermal Expansion in the temperature range of 70C. to 0 C., 5105x10 in./in.- C. (3) Thermal F.-ft.

Conductivity, 0.210.05 B.t.u.-ft./11r.-

"ice

The composition by weight percent which most closely simulated theplastic-bonded explosive is as follows:

Ingredients: Percent by weight Powdered polytetrafluoroethylene 69.8Powered linear polyamide 3.5 Pentaerythritol 26.7

The polytetrafluoroethylene used in this application is sold under thetrademark Teflon and is described in United States Patent No. 2,230,654.It has a density of 2.1--2.2 gms./cc., linear coefficient of thermalexpansion (-70 C. to 0 C.) 7.2 10- in./in.- C., and thermal stability of0.14 B.t.u.-ft./hr.- F.-ft. The linear polyamide sold under thetrademark Zytel is a nylon resin of the general type described in UnitedStates Patents 2,071,250, 2,071,254 and 2,130,948. The linear polyamideused herein has a density of 1.1 gms./cc., a linear coefficient ofthermal expansion (70 C. to 0 C.) 12.3 X 10 in./in.- C., and thermalconductivity of 0.16 B.t.u.- ft./hr.- F.-ft.

To make a fifty pound batch of the inert simulant, 1.75 lbs of Zytel 63granular (soluble grade), and 54 lbs. of methanol were placed in a fortygallon slurry kettle. Water at 125 F. was turned on in the kettle jacketand the mixture stirred moderately (100 r.p.m.) until all the Zytel 63was dissolved (60-120 minutes). Care should be taken not to exceed 115F. fluid temperature inside the kettle. When the Zytel is completelydissolved, the stirring rate should be increased to 200 r.p.m. andfirst, 34.9 lbs. of powdered Teflon, then 13.35 lbs. of pentaerythritolshould be gradually added by hand. Stirring should be continued at 200r.p.m. for another 15 minutes to completely disperse both the Teflon andthe entaerythritol. When the complete dispersion in the lacquer hastaken place, increase the stirring rate to 400 r.p.m. At this point, themixture is water quenched, and the Zytel is released from solution withthe methanol coating the pentaerythritol, while the methanol is drawn01f in solution with the quench water. A large quench of to 100 lbs. ofF.- F. water is added to initiate break-up of the mix into smallparticles. Stirring is continued at approximately 400 r.p.m. whileadding the 80 F.85 F. water as a constant rate until the kettle volumeis filled. At this point, the proper particle size is achieved. Thejacket is then drained of warm water, and 75 F.80 F. cold water is addedthrough the jacket to cool the mix. Stirring is stopped, the cold wateris turned off, and the particles are allowed to settle. The supernatantliquid is then decanted off, and the remaining water-simulant mixture ismanually withdrawn'from the kettle. The mixture is filtered for severalhours to remove additional liquid, and then oven dried overnight at F.in flat trays. The dried material should possess the following particlesize distribution: 10% will remain in a 5 mesh screen and less than 5%will pass through a 40 mesh screen.

The compositon contained about 69.8% by weight Teflon, 3.5% by weightZytel and 26.7% by weight pentaerythritol. A tabulation of the physicalproperties for the plastic bonded explosive and its inert simulantdetermined by using duplicate samples are listed below:

This composition is pressable and is presently being successfully usedfor mock warhead configurations in several missile programs and tosimulate the explosive charge of various bombs which are used inconjunction with other well developed rocket programs.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

1. An inert simulant formation for high explosive compositionscomprising an admixture of about 70 percent by weightpolytetrafluoroethylene, about 27 percent by weight pentaerythritol andabout 4i0.5 percent by weight linear polyamide to simulate a densityfrom 130010.110 gms./cc., thermal conductivity from 02:0.05 B.t.u.-ft./hr.- F.-ft. and thermal coeificient of expansion in the temperaturerange of --70 C. to C., 5i0.5 10- in./in.-C. of said explosivecomposition.

2. An inert simulant formulation for a plastic-bonded explosiveconsisting of the following:

References Cited UNITED STATES PATENTS 3,018,203 1/1962 Guth 14945 X3,108.917 10/1963 McIrvine 149105 X 3,375,122 3/1968 Roth 106204BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, Assistant ExaminerUS. Cl. X.R.

